In order to rationally determine the characteristic parameters of tunnel grouting circle under drainage mode of deep ditch, the rationality of the grouting circle parameters of a tunnel in waterrich karst area is discussed by a fluidsolid coupling calculation model based on software FLAC3D, and the influencing laws of thickness and permeability of grouting circle on water gushing volume, water pressure of lining structure and structural safety are studied. The study results show that: (1) The water pressure of lining and the water gushing volume can be reduced, and the structural safety can be guaranteed by rationally increasing the thickness of the grouting circle or reducing the permeability of the grouting circle. (2) According to the simulation results and similar projects, the thickness of grouting circle of 56 m and the permeability coefficient of 2×10-6 cm/s are recommended, respectively; and the grouting parameters should be rationally determined according to actual technoeconomic comparison results.